The present invention relates to a medical material comprising an aromatic vinyl compound/xcex1-olefin random copolymer and a medical device formed therefrom. More particularly, the present invention relates to a medical material which has not only radiation resistance but also biocompatibility, particularly blood compatibility and is excellent in the mechanical properties and transparency and which contains substantially no chlorine, and a medical device made thereof.
Medical devices such as tubes to be used for intravenous drip injection, catheters, circuits and bags or containers for bloods, infusion solutions and dialysis, are usually required to be excellent in not only flexibility, elasticity and transparency but also radiation resistance and biocompatibility, particularly blood compatibility. Further, sufficient strength durable for operations is also required. Especially, tubes are required to have proper elastic elongation and touchiness and to have so-called resilience. Heretofore, they have been produced in many cases from a soft vinyl chloride which is a base material having these properties. Further, in recent years, disposability of the medical devices has been advanced, and they are in many cases disposed by incineration treatment to prevent biohazard. With respect to medical devices wherein soft polyvinyl chloride is used, the load to the environment due to e.g. incineration is considered to be problematic, and a study is being made to substitute other materials for the soft polyvinyl chloride as the base material for medical devices.
As films and tubes containing no chlorine, those made of a linear low density ethylene/xcex1-olefin type copolymer, have been known, but there has been no medical material which fully satisfies the above conditions as a medical material. As a resin composition which is excellent in flexibility and which presents a formed product suitable for medical use, JP-A-4-159344 proposes a resin composition comprising an olefin type resin, a hydrogenation product of styrene/butadiene block copolymer and a hydrogenation product of styrene/isoprene block copolymer. This resin composition presents a formed product which is excellent in flexibility and has a feature that even if the formed product is incinerated, no toxic gas will be formed. However, the formed product obtained by such a resin composition is not yet adequate in another property i.e. transparency required for medical devices and still has a room for improvement in this respect.
Further, JP-A-3-202298 discloses that a non-soft vinyl chloride resin, specifically a composition comprising a styrene type elastomer, polypropylene, etc. or a composition of a citric acid ester, has an activity to inhibit hemolysis, and JP-A-6-319785 discloses a thermoplastic polyester type composition. However, either one is not adequate as compared with the hemolysis inhibitory action of a plasticizer in the soft vinyl chloride resin and is poor in the practical applicability.
Further, among catheters, a balloon catheter of a type whereby a balloon is expanded in a blood vessel and then shrinked to be retained for a few days, has a problem such that if the surface loosens, a blood clot is likely to result due to slackening of blood flow. A gastrointestinal catheter is repeatedly pulled by a peristaltic motion of the gastrointestinal tract. Accordingly, in such an application, it is required to be excellent in strain recovery. Thermoplastic polyurethane used for conventional catheters is excellent in mechanical properties, but has a drawback that it is poor in strain recovery.
An object of the present invention is to provide a medical product which is excellent not only in flexibility, elasticity and transparency required for medical use but also in radiation resistance and biocompatibility including blood compatibility and which is free from generation a toxic gas at the time of incineration, and a medical device made thereof.
The present inventors have conducted an extensive study to solve the above problem and as a result, have found that an aromatic vinyl/xcex1-olefin random copolymer or a resin composition having a plasticizer blended to such a copolymer in a certain amount, is suitable as a medical material or a material for a medical device, and have finally completed the present invention.
Namely, the present invention is a medical material and a medical device comprising an aromatic vinyl compound/xcex1-olefin random copolymer, preferably a medical material and a medical device, obtained by processing a resin composition (C) comprising 100 parts by weight of a resin component (A) containing at least 50 wt % of an aromatic vinyl compound/xcex1-olefin random copolymer and from 0.1 to 200 parts by weight, preferably from 0.5 to 100 parts by weight, more preferably from 1 to 50 parts by weight, of a plasticizer (B).
The medical material and the medical device of the present invention are excellent in flexibility, elasticity, transparency, radiation resistance and biocompatibility. In the present invention, a medical device is meant for a medical device to which sterilization treatment has been applied and which is to be used for medical application. A medical material is meant for a material for a medical device and is meant for e.g. a sheet (including a film and a plate) obtained by processing an aromatic vinyl compound/xcex1-olefin random copolymer or its composition (C) by e.g. extrusion stretch forming.
The aromatic vinyl compound/xcex1-olefin random copolymer to be used in the present invention, is basically a copolymer made of an aromatic vinyl compound monomer and an xcex1-olefin monomer. The structure is not particularly limited. However, for example, an aromatic vinyl compound/xcex1-olefin random copolymer obtainable by means of a metallocene catalyst of the chemical formula 1 which will be described hereinafter, has high stereo regularity and a head-to-tail chain structure of at least two aromatic vinyl compound units, whereby it is excellent in initial tensile modulus of elasticity, breaking strength, elongation, transparency and chemical resistance.
As the aromatic vinyl/xcex1-olefin random copolymer to be used in the present invention, one having a weight average molecular weight of at least 30,000, is practical.
The upper limit for the weight average molecular weight is not particularly limited, but it is preferably at most 3,000,000, more preferably at most 1,000,000. If the molecular weight exceeds 3,000,000, the melt viscosity tends to increase, whereby molding by a common molding method such as injection molding or extrusion molding tends to be difficult.
Here, the weight average molecular weight (Mw) is a molecular weight calculated as polystyrene, obtained by GPC using standard polystyrene.
Further, the molecular weight distribution (Mw/Mn) is at most 6, preferably at most 4, particularly preferably at most 3. The molecular weight distribution being small or the uniformity of the resin being high consequently contributes to good transparency of the resin.
Mn represents a number average molecular weight and can likewise be measured by a GPC method.
With the aromatic vinyl compound/xcex1-olefin random copolymer to be used in the present invention, the glass transition point (Tg) can be changed within a wide range depending upon the content of the aromatic vinyl compound. For example, with the styrene-ethylene random copolymer, Tg becomes to be close to 30xc2x0 C. at a styrene content of 50% by molar ratio. Further, by using it in combination with a thermoplastic resin having Tg of at least 30xc2x0 C, Tg as the composition can be set within a wide range, whereby the temperature dependency of viscoelasticity such as storage modulus or loss tangent (tanxcex4) can be controlled. Accordingly, in the present invention, Tg can be increased to a level close to normal temperature, if desired, by mixing a petroleum resin, a terpene resin, a cumarone-indene resin, a rosin type resin or hydrogenation derivatives thereof, having high Tg, to the aromatic vinyl compound/xcex1-olefin random copolymer, whereby it becomes easy to accomplish specific viscoelastic properties.
Especially, with a catheter to be percutaneously inserted into the body, one having Tg of from 30 to 35xc2x0 C. will be flexible in the body by the body temperature, whereby there is a merit that the possibility of damaging a human body system can be minimized.
Here, the thermoplastic resin having a glass transition temperature (Tg) of at least 30xc2x0 C. may, for example, be a petroleum resin from cyclopentadiene or its dimer or an aromatic petroleum resin from a C9 component; the terpene resin may, for example, be a terpene resin from xcex2-pinene, or a terpene/phenol resin; and the rosin type resin may, for example, be a rosin resin such as gum rosin or wood rosin, or an esterified rosin resin modified by glycerol or pentaerythritol.
These includes ones having various Tg depending upon the molecular weights. However, those having a Tg of from 30 to 100xc2x0 C., preferably from 70 to 90xc2x0 C., are preferred. With one having a Tg of lower than 30xc2x0 C., it will be necessary to mix it in a large amount in order to increase Tg depending upon the aromatic vinyl compound/xcex1-olefin random copolymer to be mixed, whereby bleeding on the surface of the medical device is likely to be brought about, and a problem may result in the mechanical strength.
The method for preparing the aromatic vinyl compound/xcex1-olefin random copolymer to be used in the present invention, is not particularly limited. However, a method of copolymerizing an aromatic vinyl compound and an xcex1-olefin in the presence of a coordination polymerization catalyst, is a preferred method for preparation.
The coordination polymerization catalyst to be used, may be a soluble Zieglar-Natta catalyst or a transition metal compound catalyst activated by methyl aluminoxane or a boron compound (so-called metallocene catalyst or half metallocene catalyst, or CGCT catalyst).
Specifically, the polymerization catalysts disclosed in the following literatures and patents can be employed.
Metallocene catalysts are disclosed in U.S. Pat. No. 5,324,800, W098/09999, JP-B-7-37488, JP-A-6-49132, Polymer Preprints, Japan, 42, 2292 (1993), Makromol. Chem., Rapid Commun., 17, 745 (1996) by the present inventors, JP-A-9-309925 and EP-0872492A2.
Half metallocene catalysts are disclosed in Makromol. Chem., 191, 2387 (1990).
GCCT catalysts are disclosed in JP-A-3-163088, JP-A-7-53618, and European Patent 416815.
The aromatic vinyl compound/xcex1-olefin random copolymer to be used in the present invention includes, for example, an aromatic vinyl compound/xcex1-olefin random copolymer obtained by means of the following transition metal compound or by the following production method. However, it is not limited by the transition metal compound or the production method of the present invention.
The aromatic vinyl compound/xcex1-olefin random copolymer to be suitably used in the present invention, can be produced from an aromatic vinyl compound and an xcex1-olefin by means of a catalyst comprising a transition metal compound of the following chemical formula 1 and a co-catalyst: 
(wherein A and B are groups selected from an unsubstituted or substituted cyclopentaphenanthryl group (the following chemical formulae 2 to 3), an unsubstituted or substituted benzindenyl group (chemical formulae 4 to 6), an unsubstituted or substituted cyclopentadienyl group (chemical formula 7), an unsubstituted or substituted indenyl group (chemical formula 8), or an unsubstituted or substituted fluorenyl group (chemical formula 9), provided that at least one of A and B is a group selected from an unsubstituted or substituted cyclopentaphenanthryl group, an unsubstituted or substituted benzindenyl group, or an unsubstituted or substituted indenyl group. Preferably, at least one of A and B is a group selected from an unsubstituted or substituted cyclopentaphenanthryl group or an unsubstituted or substituted benzindenyl group. 
(in the above chemical formulae 2 to 9, each of R1 to R8 is hydrogen, a C1-20 alkyl group, a C6-10 aryl group, a C7-20 alkylaryl group, a halogen atom, an OSiR3 group, a SiR3 group or a PR2 group (each R is a C1-10 hydrocarbon group), a plurality of Ri may be the same or different from one another.) When each of A and B is an unsubstituted or substituted cyclopentaphenanthryl group, an unsubstituted or substituted benzindenyl group or an unsubstituted or substituted indenyl group, the two may be the same or different.
In the above chemical formula 2, Y is a methylene group, a silylene group or an ethylene group, which has bonds to A and B and which has hydrogen or a C1-15 hydrocarbon group. The hydrocarbon group may, for example, be an alkyl group, an aryl group, a cycloalkyl group or a cycloaryl group. The substituents may be the same or different from one another.
Particularly preferably, Y is, for example, xe2x80x94CH2xe2x80x94, xe2x80x94CMe2xe2x80x94, xe2x80x94CEt2xe2x80x94, xe2x80x94CPh2xe2x80x94, a cyclohexylidene or cyclopentylidene group. Here, Me represents a methyl group, Et an ethyl group, and Ph a phenyl group.
In the above chemical formula 2, X is hydrogen, halogen, a C1-15 alkyl group, a C6-10 aryl group, a C8-12 alkylaryl group, a silyl group having a C1-4 hydrocarbon substituent, a C1-10 alkoxy group, or a dialkylamide group having a C1-6 alkyl substituent. The halogen may, for example, be chlorine or bromine; the alkyl group may, for example, be a methyl or ethyl; the aryl group may, for example, be a phenyl group; the alkylaryl group may, for example, be a benzyl group; the silyl group may, for example, be a trimethylsilyl group; the alkoxy group may, for example, be a methoxy group, an ethyoxy group or an isopropoxy group; and the dialkylamide group may, for example, be a dimethylamide group.
M is zirconium, hafnium or titanium. Particularly preferred is zirconium.
The co-catalyst to be used in the present invention may be a co-catalyst which has heretofore been commonly used in combination with a transition metal compound. As such a co-catalyst, aluminoxane (or alumoxane) or a boron compound is suitably used.
Such a boron compound and the above organic aluminum compound may be used at the same time. Especially when a boron compound is used as a co-catalyst, it is effective to add an alkyl aluminum compound such as triisobutylaluminum in order to remove impurities which adversely affect polymerization, such as water contained in the polymerization system.
The aromatic vinyl compound constituting the aromatic vinyl compound/xcex1-olefin random copolymer to be used in the present invention, may, for example, be styrene and various substituted styrenes, such as p-methylstyrene, m-methylstyrene, o-methylstyrene, o-t-butylstyrene, m-t-butylstyrene, p-t-butylstyrene and xcex1-methylstyren. These compounds may be used in combination. Further, a compound having a plurality of vinyl groups in one molecule, such as divinylbenzene, may be mentioned.
Industrially preferred is styrene or p-methylstyrene, and particularly preferably, styrene is employed.
The xcex1-olefin constituting the aromatic vinyl compound/xcex1-olefin random copolymer to be used in the present invention may suitably be a C2-20 xcex1-olefin, such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, or a cyclic olefin such as norbornene or norbornadiene. Further, these olefins may be used in combination of two or more of them.
Industrially, ethylene or propylene is preferred, particularly preferably, ethylene is employed.
As a production method for the aromatic vinyl compound/xcex1-olefin copolymer as described here, a known method may be employed wherein the above exemplified xcex1-olefin, the aromatic vinyl compound and the catalyst are contacted at a certain predetermined temperature.
The polymerization method is not particularly limited, and it may, for example, be a method for bulk polymerization in a liquid monomer or a method for solution polymerization in a single or mixed solvent selected from a saturated aliphatic or aromatic hydrocarbon or a halogenated hydrocarbon, such as pentane, hexane, heptane, cyclohexane, benzene, toluene, xylene, chloro-substituted benzene, chloro-substituted toluene, methylene chloride or chloroform. Further, the polymerization type may suitably be selected from batch polymerization, continuous polymerization, batch type polymerization, preliminary polymerization or gas phase polymerization, or a combination thereof.
The polymerization temperature for the aromatic vinyl compound/xcex1-olefin copolymer using a transition metal compound as a catalyst, is properly from xe2x88x9278xc2x0 C. to 200xc2x0 C., preferably from 0 xc2x0 C. to 160 xc2x0 C. The polymerization temperature lower than xe2x88x9278xc2x0 C. is industrially disadvantageous, and if it exceeds 200xc2x0 C., decomposition of the transition metal compound tends to take place, such being undesirable. Further, industrially particularly preferably, it is from 30xc2x0 C. to 160xc2x0 C.
The amount of the transition metal compound to be used, is preferably such that the molar ratio of double bonds of the total charged monomers to the transition metal atoms in the transition metal compound, i.e. the molar ratio of double bonds of the total charged monomers/transition metal atoms, is from 1 to 108.
When methyl alumoxane is used as the co-catalyst, the molar ratio of aluminum atoms in the methyl alumoxane to the transition metal atoms in the transition metal compound i.e. the molar ratio of aluminum atoms/transition metal atoms is from 0.1 to 100,000, preferably from 10 to 10,000.
When a boron compound is used as the co-catalyst, it is employed in a molar ratio of boron atoms/transition metal atoms of from 0.01 to 100, preferably from 0.1 to 10. If the molar ratio is smaller than this range, the transition metal compound can not be effectively activated, and if it exceeds this range, such will be economically disadvantageous.
The transition metal compound and the co-catalyst may be mixed or formulated outside the polymerization tank or may be mixed in the tank at the time of polymerization.
As an example, the random copolymer produced by means of the transition metal compound as described above, has characteristics in its chain structure and stereo regularity, and the details are disclosed in EP-A-0872429A2 or JP-A-9-309925 by the present inventors. Also with respect to the transition metal compound catalyst and the co-catalyst to be employed for the production, details are disclosed in the same publications.
Further, for the aromatic vinyl compound/xcex1-olefin random copolymer obtained by this method, the amount of the catalyst used in the polymerization is very small, and accordingly, the catalyst component remaining in the formed copolymer is also extremely little, and the residual impurities are accordingly little, and also from this aspect, it is preferred that in the medical use, a medical material and a medical device with a high level of safety can be provided.
Of the aromatic vinyl compound/xcex1-olefin random copolymer to be used in the present invention, the constituting components are not necessarily limited only to the aromatic vinyl compound and the xcex1-olefin, and other monomers may be copolymerized, within a range not to impair the performance. Other monomers to be copolymerized may, for example, be a C3-20 xcex1-olefin such as propylene other than those selected above, a C5-20 cyclic olefin such as norbornene, or a diene compound such as butadiene, 1,4-hexadiene, 1,5-hexadiene, ethylidene norbornene or vinyl cyclohexene. Further, two or more types of the above mentioned aromatic vinyl compounds may be copolymerized.
Further, depending upon the polymerization conditions, etc., the aromatic vinyl compound may contain a small amount of an atactic homopolymer formed by thermal, radical or cationic polymerization. However, such an amount is not higher than 10 wt % of the whole, and such a homopolymer can be removed by solvent extraction. However, if there is no particular problem from the viewpoint of the physical properties, the material may be used as it contains such a homopolymer.
In the medical material and the medical device of the present invention, a plasticizer (B) is blended to the resin component (A) for the purpose of adjusting the flexibility, the temperature dependency of physical properties, etc. As such a plasticizer, a known-plasticizer may be employed. For example, it is possible to add at least one member selected from a phthalic acid ester, a pyromellitic acid ester, a trimellitic acid ester, a trimesinic acid ester, a benzoic acid ester, an adipic acid ester, an azelaic acid ester, a sebacic acid ester, a malic acid ester compound, an epoxy compound, a polyester compound and an aromatic or aliphatic hydrocarbon oil.
As a preferred plasticizer, a low molecular weight organic ester type compound and a hydrocarbon may be employed. Among them, particularly preferred are the following phthalic acid ester type plasticizers.
Taking into consideration the bleeding property, influences over the human bodies, etc. totally, specific examples of preferred plasticizers may be dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di-n-octyl phthalate, di-n-decyl phthalate, di-n-lauryl phthalate, undecyl phthalate, tetra-n-octyl pyromellitate, tri-n-octyl pyromellitate, triisooctyl trimellitate, tri-2-ethylhexyl trimellitate, trimellisic acid tri(2,2-dimethylpentyl)ester, trimesic acid tri(2-ethylhexyl)ester, benzoic acid diester, di-2-ethylhexyl adipate, diisodecyl adipate, dicapryl adipate, di-2-ethylhexyl azelate, di-2-ethylhexyl sebacate, dibutyl sebacate, tricresyl phosphate, triphenyl phosphate, diphenylcresyl phosphate, tributyl phosphate, dioctyl epoxyhexahydrophthalate, epoxidized soybean oil, methyl epoxy stearate, adipic acid type polyester, and sebacic type polyester.
With respect to the molecular weight of the plasticizer (B), there is no particular limitation. However, with respect to a low molecular organic ester type compound, it is preferably from 250 to 800, more preferably from 300 to 600.
If the molecular weight is too low, there will be a problem of volatilization, and if the molecular weight is too high, the molecules tend to hardly move in the composition, and particularly in the application to a blood bag, it tends to hardly elute into an erythrocyte-containing liquid, and consequently, an action to protect erythrocytes (hemolysis inhibition action) tends to be small.
The amount of the plasticizer (B) to be blended is from 0.1 to 200 parts by weight, preferably from 0.5 to 100 parts by weight, more preferably from 1 to 50 parts by weight, per 100 parts by weight of the resin composition (A) containing the aromatic vinyl compound/xcex1-olefin random copolymer.
Further, for a blood bag, addition of a plasticizer is preferred from the viewpoint of the hemolysis inhibition action.
In the medical material and the medical device of the present invention, other thermoplastic resins may be incorporated in the resin component (A) constituting them, within a range of at most 50 wt %, as the case requires.
The thermoplastic resins to be blended are not particularly limited, and a styrene type resin, an olefin type resin, a polyester such as polycarbonate, polyethylene phthalate or polybutylene phthalate, an aromatic resin such as polyphenylene ether (PPE) or polyphenylene sulfide (PPS), a polyamide such as 6,6-nylon or 6-nylon, a methacrylic resin, an acrylic resin, an ethylene/vinyl acetate copolymer, a polymer such as EVA, or an elastomer or rubber, may be blended.
The styrene type resin may specifically be, for example, polystyrene, rubber-reinforced polystyrene (high impact polystyrene), an acrylonitril/styrene copolymer (AS resin), a styrene/mathacrylate copolymer such as a styrene/methyl methacrylate copolymer (MS resin), an acrylonitrile/butadiene/styrene copolymer (ABS resin), a rubber-reinforced MS resin, a maleic anhydride/styrene copolymer, a maleic anhydride/acrylonitrile/styrene copolymer, an acrylonitrile/a-methyl styrene copolymer, a methacrylnitrile/styrene copolymer or a methyl methacrylate/acrylonitrile/styrene copolymer.
The olefin type resin may specifically be, for example, a homopolymer such as polyethylene (PE) or polypropylene (PP), a block or random copolymer with butene, hexene, octene or the like, polymethylpentene, polybutene-1, a propylene/butene-1 copolymer, an ethylene/methacrylic acid or its ester copolymer, an ethylene/acrylic acid or its ester copolymer, or an ethylene/propylene copolymer (EPR).
The methacrylic resin may specifically be, for example, polymethacrylate (PMMA) or a methyl methacrylate/methacrylic acid copolymer.
Among the above, a styrene type resin or an olefin type resin is particularly preferred.
In the present invention, the elastomer or rubber to be blended, is not particularly limited. A styrene type or olefin type thermoplastic elastomer, and a thermoplastic elastomer or rubber, such as rubber, natural rubber, isoprene rubber, polyisobutyrene, EPR, acrylic rubber, neoprene rubber, polyester type elastomer or polyamide type elastomer, may, for example, be mentioned. These materials may be used alone or in combination of a plurality of them.
Examples of the styrene type elastomer or rubber include a styrene/butadiene block copolymer (SBS), a styrene/isoprene block copolymer (SIS) and hydrogenation products thereof, such as styrene/ethylene/butylene block copolymer (SEBS), a styrene/ethylene/propylene block polymer (SEPS), a styrene/butadiene rubber (SBR) and a styrene/butadiene/methyl methacrylate copolymer (MBS).
Among them, particularly preferred is a styrene type or olefin type elastomer or rubber. Further, the medical material or a medical device of the present invention may be used as closslinked by a conventional closslinking method by means of e.g. a peroxide or electron beam, as the case requires.
Further, a modification such as grafting, hydrogenation or addition of a functional group may be made to the aromatic vinyl compound/xcex1-olefin random copolymer to be used for the medical material or the medical device of the present invention, by a conventional technique in this field. With respect to the medical material or the medical device of the present invention, such as a tube, a catheter, a bag or a container, an anti-fogging agent may be incorporated to the resin composition (C) prior to molding, which comprises the resin component (A) and the plasticizer (B), as the case requires, for the purpose of preventing fogging of the medical device by condensation of moisture in air on its surface to make it difficult to see the content. Otherwise, a method of coating such an anti-fogging agent on the surface of the medical device may also be effective.
As the anti-fogging agent, one commonly employed may be used as it is. For example, a sorbitan fatty acid ester, a glycerol fatty acid ester, a polyglycerol fatty acid ester, a fatty acid amine or a fatty acid amide may be mentioned.
Among them, a glycerol fatty acid ester, a polyglycerol fatty acid ester, a polyoxyalkylene ether or a fatty acid amine is particularly preferred.
The amount of the anti-fogging agent is at most 10 parts by weight, preferably from 0.5 to 8 parts by weight, more preferably from 1 to 5 parts by weight, par 100 parts by weight of the resin composition (C).
With respect to the medical material or the medical device of the present invention, various additives such as an antioxidant, an ultra violet absorber, a light stabilizer and a colorant, may be added to the resin composition (C), as the case requires. The amount of such additives is usually within a range of at most 5 parts by weight per 100 parts by weight of the resin composition (C).
In its application, the medical material or the medical device is used in various forms such as a film, a sheet, a catheter, a tube, a container, etc. The required mechanical strength varies depending upon the respective applications.
For the medical material or the medical device comprising the aromatic vinyl compound/xcex1-olefin random copolymer of the present invention, it is possible to provide a medical material or the medical device having a wide range of physical properties by changing the content of the aromatic vinyl compound in the copolymer and the amount of the plasticizer incorporated.
For example, a nutrition catheter is required to have flexibility and low hardness to facilitate its insertion into the body. Further, the tube will be pulled repeated by the peristaltic motion, and accordingly, if the permanent elongation of the material is large, the surface tends to loosen to cause slackening of blood flow, which is likely to cause a blood clot. Therefore, the copolymer is desired to be one having a breaking elongation of at least 200% and a permanent elongation of at most 60%. For example, copolymers P-1 to P-3, which will be described hereinafter, may be mentioned. In a case where it is required to see the content, transparency will be required, and copolymers P-6 to P-8 may, for example, be mentioned.
When the above mentioned aromatic vinyl/xcex1-olefin random copolymer obtainable by means of a transition metal compound of the chemical formula 1 as described above, is employed, the medical material or the medical device of the present invention is excellent in flexibility and particularly excellent in transparency and thus shows a haze value of at most 20% when made into a sheet having a thickness of e.g. 1 mm.
Heretofore, a medical device made of soft vinyl chloride has been sterilized usually by means of ethylene oxide gas (EOG). However, an adverse effect to the patient due to the remaining EOG is worried, and it is desired to eliminate the influence of the remaining EOG, and switching to other sterilization methods is conceivable. To the medical material or the medical device of the present invention, a gamma ray sterilization method can be applied, which is preferred in that no residue will remain by this method. The gamma ray sterilization method is convenient in that a closslinking reaction can be carried out at the same time as sterilization. Further, the medical material or the medical device of the present invention provides good biocompatibility. It is particularly excellent in blood compatibility. Especially in an application for insertion into a blood vessel, the medical device of the present invention is capable of imparting an antithrombotic property to its wetted surface. As a method of imparting the antithrombotic property, a known method may be employed. For example, e.g. heparine or urokinase may be fixed to the reactive functional groups of the catheter base material by covalent bonds, ionic bonds or adsorption.
With respect to the medical material or the medical device of the present invention, a method to obtain the resin composition (C) prior to molding, i.e. a method to obtain a resin composition (C) by mixing the resin component (A) and the plasticizer (B), and if necessary, other additives, is not particularly limited, and a conventional technique may be employed. For example, dry blending can be carried out by means of e.g. a Henschel mixer, a ribbon blender, a super mixer or a tumbler, or melt mixing may be carried out by means of a single screw or twin screw extruder, a Banbury mixer, a plastmill, a co-kneader or a roll mill. If necessary, such a method can be carried out in an inert gas atmosphere such as nitrogen. The form may be selected from e.g. a powder form, a pellet form, a strand form or a chip form.
In the present invention, a method for producing a medical device from the resin composition (C) may suitably be selected depending upon the shape of the medical device. For example, a known forming method such as extrusion molding, injection molding, compression molding, blow molding, rotational molding, calender forming, thermoforming or cast molding may be mentioned. A plurality of forming methods may be used in combination.
For the production of a multilayer sheet, a lamination method may also be employed. Further, in order to prevent blocking between sheets, the inner surface or the outer surface of a container may be roughened i.e. embossed, or an anti-blocking agent or a slipping agent may, for example, be added.
In either forming method, the principle of the method is such that the material is heated, melted or softened, whereupon it is deformed by an external force to a desired shape, and the fluidity of the material and the behavior in the molding process by the external force will influence over the physical properties of the formed product. Incorporation of a plasticizer serves effectively to improve such forming properties.
When the medical device of the present invention is, for example, a blood bag, an infusion solution bag or a dialysis bag, the sheet material for such a bag may be a single layer or a laminate containing the resin composition comprising the resin component (A) and the plasticizer (B), as a formed layer. This means that the sheet material may be composed solely of the resin composition (C) in the present invention or may be a laminate comprising at least one layer made of the resin composition (C) and at least one layer made of other resin component.
In the case of a laminate, layers made of other resin components are used for the purpose of the adjusting or improving e.g. the mechanical properties, forming properties, heat sealing properties, blocking resistance and heat resistance of the bag.
The resin components for forming the layers of other resin components, as the resin components for forming layers of a laminate, may, for example, be polyethylene, an ethylene/vinyl acetate copolymer, an ethylene/acrylate copolymer, polypropylene, poly-4-methylpentene-1, polyamide, polyether amide (a block copolymer of polyether and polyamide), polyurethane and a thermoplastic polyester.
In the laminate, the thicknesses of the polymer layers as formed layers, are important. Especially, in the case of a blood bag, leaching out of the plasticizer component (B) is important when other resin component is used as a formed layer for the inner layer which is in contact with the blood, and the layer should better be as thin as possible within an allowable range, preferably at most 0.08 mm, more preferably at most 0.05 mm.
When used for a laminate, the amount of the plasticizer (B) is selected particularly within a range of from 5 to 50 parts by weight in the range as described above, although it varies depending upon the types of the resin component (A) and the plasticizer component (B), or upon a single layer or laminate. Further, in the case of a laminate, the plasticizer component (B) should preferably be relatively large in amount. Further, the thickness of the entire sheet constituting the bag is preferably from 0.08 to 0.6 mm, more preferably from 0.1 to 0.5 mm, from the viewpoint of the strength, processability and operation efficiency.
Now, medical devices according to the present invention will be described.
Medical devices such as catheters to be inserted into a respiratory tract, a trachea, a digestive tract, a urethra, a blood vessel or other body cavities or systems, are required to have smoothness so that they can be certainly inserted to the desired sites without damaging the systems. Further, coating of a lubricative resin may be formed on the entire surface of the base material when an excellent lubricity is required on the surface in order to avoid damages to a mucous membrane or inflammation due to friction during the retention in the system. For example, such coating may be formed by covalent bonding of a water soluble polymer such as a maleic anhydride type polymer.
Utilizing the above described characteristics, the medical devices of the present are used, for example, as medical devices such as catheters e.g. indwelling catheters or balloon catheters, artificial blood vessels, circuits, syringes, artificial dialysers, blood component separators, artificial lungs or wound dressings, or as medical products such as sanitary goods e.g. menstrual sanitary products or paper diapers, surgical clothings or disposable sheets for hospital use. Among them, they are preferably used as medical devices to be used in contact with a body fluid, especially blood, such as medical tubes, catheters, artificial blood vessels, circuits, syringes, blood dialysers, blood component separators or artificial lungs, utilizing their excellent biocompatibility. With these medical devices, it is not necessary that the entire portion is formed of the medical material of the present invention, and it is sufficient that at least the portion which is in contact with the body fluid is formed of the medical material of the present invention. For example, with the above mentioned tubes, catheters or blood bags, the portion which is in contact with the body fluid is formed by the medical material of the present invention, and a portion which is not in contact with the body fluid may be formed of another resin to be used for medical use, such as polyurethane. Further, a medical container may be mentioned as one of the medical devices of the present invention, and it is preferably employed in an application where excellent flexibility and transparency are required.
The medical devices will be exemplified more specifically.
A. Intravascular insertion or indwelling catheters such as angiography catheters, cerebrovascular treating catheters, thermodilution catheters, IVH catheters or indwelling needles, or directers, stylettes, introducers or guide wires for these catheters.
B. Various balloons or balloon catheters.
C. Catheters to be orally or nasally inserted or retained in digestive organs, such as gastric tube catheters, nutrition catheters or tubes for supplying nutrition.
D. Oxygen catheter, oxygen cannula, tubes or cuffs for endotracheal tubes, tubes or cuffs for tracheotomy tubes, or catheters to be orally or nasally inserted or retained, such as endotracheal suction catheters.
E. Catheters to be inserted or retained in various body cavities or systems, such as suction catheters, waste liquid catheters, abdominal catheters, rectum catheters, urethral catheters or trocar tubes.
F. Endoscopic tubes to be inserted in various body cavities.
G. Stents, or artificial blood vessels, artificial tracheae, artificial bronchial tubes or artificial anus.
H. Various medical appliances such as artificial lungs, artificial hearts, artificial kidneys, reservoirs, bubble traps or drip chambers, or hearts to constitute extracorporeal circulation circuits such as circuit tubes forming blood flow paths.
I. Bags such as blood bags, infusion solution bags, injection liquid bags or waste liquid bags, or parts such as tubes or connectors to be connected to such bags.
J. Inspection instruments or treatment instruments which are required to have low friction resistance (lubricity) during retention in the bodies or during sliding, or inspection instruments or treatment instruments which are required to have antithrombotic properties.
K. Various gas supply tubes, or liquid supply tubes.
L. Contact lenses.
Now, the present invention will be described in further detail with reference to Examples. However, these Examples by no means restrict the present invention.
In the following description, Ind represents a 1-indenyl group, BInd a 4,5-benz-1-indenyl group, CpPhen a 3-cyclopenta[c] phenanthrene group, Flu a 9-fluorenyl group, Me a methyl group, Et an ethyl group, tBu a tertiary butyl group, and Ph a phenyl group.
The analyses of copolymers obtained in various Examples and Comparative Examples were carried out by the following methods, and 13C-NMR spectra were measured by means of xcex1-500 or JNMGX-270, manufactured by Nippon Denshi KK using a deuterated chloroform solvent or a deuterated 1,1,2,2-tetrachloroethane solvent and using TMS as standard.
Here, the measurement using TMS as standard is the following measurement. Firstly, using TMS as standard, a shift value of the center peak of the triplet 13C-NMR peak of deuterated 1,1,2,2-tetrachloroethane was determined. Then, the copolymer was dissolved in deuterated 1,1,2,2-tetrachloroethane, and 13C-NMR was measured, and various peak shift values were calculated using the triplet center peak of deuterated 1,1,2,2-tetrachloroethane as standard. The shift value of the triplet center peak of deuterated 1,1,2,2-tetrachloroethane was 73.89 ppm.
The 13C-NMR spectrum measurement for determination of a peak area was carried out by a NOE eliminated proton gate decoupling method using a pulse with a pulse width of 45xc2x0 and a repetition time of 5 seconds as standard.
Whereas, the measurement was tried under the same conditions by changing the repetition time to 1.5 seconds, whereby the obtained value of the peak area of the copolymer agreed to the case where the repetition time was 5 seconds, at an error tolerance level.
Determination of the styrene content in the copolymer was carried out by 1H-NMR, and as the instrument, a-500 manufactured by Nippon Denshi KK and AC-250 manufactured by BRUCKER CO. using a deuterated chloroform solvent or a deuterated 1,1,2,2-tetrachloroethane solvent and TMS as standard, the comparison of intensities of the peak (6.5-7.5 ppm) attributable to a phenyl group proton and the proton peak (0.8-3 ppm) attributable to an alkyl group, was carried out.
With respect to the molecular weights in Examples, weight average molecular weights as calculated as standard polystyrene were obtained by means of GPC (gel permeation chromatography).
A copolymer soluble in THF at room temperature, was measured by HLC-8020, manufactured by TOSOH CORPORATION employing THF as the solvent.
A copolymer insoluble in THF at room temperature, was measured by 150CV apparatus manufactured by Waters Co. at 135xc2x0 C using 1,2,4-trichlorobenzene as a solvent.
The DSC measurement was carried out by means of DSC200 manufactured by Seiko Denshi KK in a N2 stream at a temperature raising rate of 10xc2x0 C./min.
The mechanical strength, flexibility, transparency and biocompatibility of the copolymers and the resin compositions obtained in Examples were carried out by the following methods, respectively.
Mechanical Strength of a Formed Product
A sheet having a thickness of 1 mm was prepared, and from this sheet, a JIS No.2 test piece was punched out. Using this test piece, the tensile modulus, the breaking elongation, the yield point strength, the breaking strength, the 100% modulus and the 300% modulus were obtained at a tensile speed of 100 mm/min and used as indices for the mechanical strength.
Permanent Elongation
A sample pressed to a thickness of 1 mm as mentioned above, was punched out into a No.2 dumbbell, which was stretched 100% (2 cm) between the marked lines of 1 cm and maintained as stretched for 10 minutes, whereupon it was released and left to stand for 10 minutes, and the length between the reference lines was measured to determine the residual permanent strain. The permanent elongation was represented by the ratio (%) of the elongation to the initial length.
Flexibility
A sheet having a thickness of 2 mm was prepared, and in accordance with a dulometer hardness testing method of JIS K-7215, dulometer hardness of types D and A was obtained and used as an index for flexibility.
Transparency of a Formed Product
A sheet having a thickness of 1 mm was prepared, and the haze was obtained by means of a turbidity meter NDH-2000, manufactured by Nippon Denshoku KK by a method prescribed in JIS K-7361-1.
MFR
Was measured in accordance with a thermoplastic flow test method of JIS K-7210. The measurement was carried out at a measuring temperature of 200xc2x0 C. under a test load of 5 kgf.
Blood Compatibility
A sheet having a thickness of 1 mm was prepared, and the obtained sheet was cut into a size of 1 cmxc3x971 cm to obtain a test piece. This test piece was immersed at 37xc2x0 C. for 30 minutes in a heparin-added whole blood prepared by adding heparin sodium salt to human blood after blood sampling, to bring the concentration to 5 IU/ml. This test piece was taken out from the heparin-added whole blood and washed with a physiological sodium chloride aqueous solution. Then, the surface was treated by means of glutaraldehyde and osmium oxide for fixing, and the obtained sample was inspected by means of an electron microscope, whereby the number of blood platelets deposited on the surface of the test piece was counted and used as an index for blood compatibility. The smaller the number of blood platelets deposited on the surface of the test specimen, the better the blood compatibility.